Users can also send a real-time display of their heartbeat to another Apple Watch.

Miura's colleague Hisanori Kogure, 35, joked to him "I'll send you my pulse", to which Mr Miura replied: "No, thank you." IT worker Ahi To, 24, had dropped in at the Apple shop to see "the newest gadget" on his way to work and said he was taken by the possibility of wirelessly connecting it to an iPhone.

Prices will start at US$349, with a limited-edition gold version costing US$10,000.

Tech firms are betting heavily on wearables as the next frontier in consumer electronics, with offerings from Motorola and Samsung, amongst others, joining the fray.

Luxury Swiss watchmaker TAG Heuer announced last month it was joining forces with Google and Intel to develop a rival to the Apple Watch.